1. Field of the Invention
This invention relates to an optical recording medium in which information signals are optically recorded and a signal recording method for recording information in the optical recording medium.
2. Description of the Related Art
For optical recording media, such as compact discs (CDs), for optical recording information signals like speech signals and data in a predetermined information recording area therein and for reproducing the recorded information signals, several techniques have been attempted for preventing pirated editions.
For example, a technique of inserting cryptogram in information signals to be recorded on the compact disc is employed.
Meanwhile, by reading the entire recorded information with a reproducing device, it is possible to easily copy the compact disc on which information signals are recorded by the foregoing technique. Thus, a compact disc which is apparently identical to the original one may be produced.
As a method for determining whether a compact disc is of the pirated edition or not, a technique of recording a pattern like a bar code or characters in an area other than the information recording area, that is, in an area in which information signals are not recorded is employed. With this technique, the copyright reserved is clarified. However, since the pattern like a bar code or characters in the above technique permits discriminating the contents simply by viewing, the same pattern of bar code or characters may easily be recorded on a compact disc of pirated edition. Accordingly, the compact disc of pirated edition may easily be produced.